The cool-flow technology is described as a 'milestone' in hydraulic expansion technology: The coolant jet is immediately forwarded through the slim precision toolholder to the tool.

Hydraulic Expansion Toolholder with Flow-Cooling

Dec. 26, 2019
Coolant or water jet does not depend on the unclamped length, always optimally adapts to the metal-cutting process.

SCHUNK has updated its Tendo Slim 4ax hydraulic expansion toolholder device with "cool-flow" technology, for effective cooling via tool mountings. Introduced three years ago, the Tendo Slim 4ax has the outside geometry of heat-shrinking mountings, according to DIN 69882-8, with Schunk's proven hydraulic expansion technology.

Now, the Tendo Slim 4ax cool-flow toolholder offers various advantages for machining steel, aluminum, and plastic. The coolant or water jet does not depend on the unclamped length and always optimally adapts to the metal-cutting process. In contrast to heat-shrinking mountings, the jet of the Tendo does not bounce back along the whole unclamped length of the tool shank, but instead fully surrounds the tool shank up to the cutting edge. This is a benefit for cooling the cutting edge, improving the chip removal, and increasing efficiency of the overall process.
Pilot applications during toolmaking show that the vibration-absorbing mounting cool-flow technology pays off with excellent surface quality when roughing, pre-finishing and finishing. Also, reworking measures and tool costs are reduced.

In contrast to heat-shrinking toolholders, the Tendo Slim 4ax seamlessly fits into Schunk's hydraulic expansion technology with its permanently precise run-out accuracy of < 0.003 mm at an unclamped length of 2.5 x D, and a balancing grade of G 2.5 at 25,000 RPM.

Moreover, the shape and positional tolerances can be met with accuracy.

The Tendo Slim 4ax also is proven in terms of perfect vibration damping and a rapid tool change by using an Allen key. There is no need to invest in expensive peripheral equipment.

Since the precision mounting of conventional heat shrinking toolholders can be replaced by Plug-&-Work without having to reprogram the outside contour, their advantages can be directly tested or permanently used.

The slim mounting with cool-flow technology will be available in 90-mm and 120-mm lengths for the HSK-A63 interfaces between ø 6 mm, up to ø 32 mm. The interfaces for SK 40 with ø 6 mm up to ø 32 mm will be available in mid-2020. Other interfaces, such as BT 40 and length variants with 160 mm, are being planned. Learn more at

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